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BQ25792: BQ25792 About default charge current

eso18
Prodigy 150 points
Part Number: BQ25792
Other Parts Discussed in Thread: BQSTUDIO, EV2400,

Hi team,

I am using a 4s2p (Nominal 14.8V) battery. My charging input voltage is 12V. BQ25792 works as boost converter for charging.

Normally the default battery charging current is 1A. But BQ25792 charges at 500 mA. As far as I understand, it reduces the charging current by half. I set the PROG pin to 750Khz. I did not make any settings via I2C.

Additionally, when I set my input voltage to 19V, the IC works as a buck converter. The battery charging current appears to be 1A. I think it works correctly this way.

Why does the battery charging current drop to 500mA at 12V input voltage? Could there be a problem with the boost converter? Do you have a suggestion?

Thank you

  • 0
    TI__Guru**** 166176 points

    Hi Eso,

    What is the input current limit setting?  If your battery is at 14.8V and you want 1A charge current with 12V input, then input current limit must be higher than 14.8V*1A/12V = 1.23A.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 150 points

    Hi Jeff 

    My input source is 12V 3A adjustable source. Actually , calculation is correct. For example now testing,  İn charging process, Input source is 12.4V 1.21A.

    Charge current is 822mA

    I connected the EV2400 module to see the data via the BQSTUDIO application. When there is a 12V input source, the "ADC IBAT" register appears to be 450mA on the BQSTUDIO. I also connected an ammeter to the battery. The ammeter shows 820 mA.

    Why does ADC show  450mA on BQstudio application?

    @Charge current setting is 2A  but battery doesnt draw 2A

    @ İnput source is 12.5V

    @ input source 19V

  • 0 in reply to eso18
    TI__Guru**** 166176 points

    Hi eso,

    Can you show me the status and fault registers from the 8-bit tab?

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 150 points

    Hi Jeff

    According to calculation, ADC is reading incorrectly,  ( 12 V * 1,28 A) / 16,4V  = 0,936 A 

    I think, the switching signal seems to be OK, but when boosting it is not reading or adjusting the current properly. strange situation :)

    There might be something I missed.

    1. picture: ADC Registers

    2.Charger setting registers

    SW2 pin of BQ25792, scope picture

  • 0 in reply to eso18
    TI__Guru**** 166176 points

    Hi Eso,

    Are you using a BQ25792EVM or your own board?  If your own board, did you follow the recommended PCB layout in the datasheet and EVM user's guide?

    Regards,

    Jeff